This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. This project identifies types/levels of polybrominated diphenyl ether (PBDE) congeners in zooplankton and muscle tissue of forage fish species from two Southeast Alaska estuaries, one with localized, the another with remote sources of PBDEs (Lemon Creek and the Peterson Creek estuaries). Extracts from whole bodies of zooplankton and tissue samples from forage fish collected from the estuaries are analyzed for PBDE levels and congener distribution. The concentration data are used in conjunction with PBDE levels previously determined in sediments and bivalves from the same estuaries to determine trophic magnification factors (TMF). Analysis of trophic level variations in congener distributions and concentrations indicate how PBDE congener distributions change as they move through environmental matrices. TMF data are used to explore toxicities of environmentally relevant mixtures of PBDEs. Toxic equivalency factors (TEFs) are used to estimate total toxicity equivalence (TEQ) of PBDE congener mixtures associated with each trophic level. Limited numbers of TEF values for PBDE congeners are available in the literature so this study utilizes TEF values for structurally analogous chlorinated compounds when necessary. TEQs indicate toxicities of mixtures of related substances and contribute valuable insights regarding threats to commercial fish and wildlife from synergistic effects among PBDE congeners. These data will be used to 1) evaluate trophic magnification factors for PBDE congeners and 2) assess toxicities of environmental mixtures resulting from attenuation of PBDEs under environmental conditions and 3) assess threats posed by remote and local PBDE sources to human health.